Friday, February 22. 2008

Rory Cellan-Jones writes today about the decling Facebook population on the BBC Technology Blog

Facebook - it's so over. That's been the tenor of most of the commentary since Thursday's figures showing a slight dip in Facebook's UK users. The general feeling is that the kids, with their minute attention spans, have already tired of the social networking site and moved on to something more hip and happening. I think the opposite is true - that Facebook's new wave of older users have decided it is just not worth the bother and are now leaving it to the kids.

Thats possible, we've noted before that the mavens are leaving Facebook (and appear to be going onto Twitter) - but it could be something much more mundane, ie just a slowdown in growth, which is never smooth.

But I wonder if most people understand what this slowdown means for something like a Social Network, where usage is heavily front-loaded.

Consider the chart below - of the 100% of time most people spend on any one social network, most is in the early days - setting up the friends, playing with the features etc - and then erodes over time. Below is a theoretical graph, showing an average halving of activity every 3 months over the 2 years average time that a person exists on a social network in any meaningful way. (Note - I don't mean people necessarily leave after 2 years, just that activity - on average - is fairly low. You can make less extreme power laws if you like, but the result described below is much the same until a fairly low tailoff rate is assumed)

Social Network Usage by quarter in % total usage

Now imagine how that curve works in a Social Network that grows from next to nothing to say 50m users over 4 years until growth tails off. As you can see, the traffic initially grows far faster than the new user growth, so its boomtime in impressionsville....but as growth starts to slow down those users' reduced activity starts to kick in, and the great crash in usage traffic then kicks in (see below).

Users (blue line) verses Usage (red line) over Life of Social Network

"Usage" above is shown as an imaginary unit so the 2 curves are easy to juxtapose.....Users are cumulative users in millions.

Now clearly this is a theoretical model, and any real-life Social Network will be adding all sorts of features to keep the traffic going, but as this quick analysis shows, when growth slows down life starts to get very........ interesting.

UPDATE 2 - now this is interesting, Facebook insists that unique visitors are still rising - which of course, is highly consistent with usage falling, following the discussion above - its just that they are not rising now as quickly as existing users' usage is decaying.

UPDATE 3 - its now Wed 26th, and Fox News now reports that Facebook hes begun its "death spiral". AllFacebook naturally disagrees, but I don't think the AllFacebois "get" the dynamics outlined above, reading their article.

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